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Date: Sun, 8 Aug 2021 11:23:08 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Zi Yan <ziy@...dia.com>
Cc: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
Matthew Wilcox <willy@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Mike Kravetz <mike.kravetz@...cle.com>,
Michal Hocko <mhocko@...nel.org>,
John Hubbard <jhubbard@...dia.com>,
linux-kernel@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Christoph Lameter <cl@...ux.com>,
Quentin Perret <qperret@...gle.com>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu
Subject: Re: [RFC PATCH 14/15] mm: introduce MIN_MAX_ORDER to replace
MAX_ORDER as compile time constant.
On Thu, Aug 05, 2021 at 03:02:52PM -0400, Zi Yan wrote:
> From: Zi Yan <ziy@...dia.com>
>
> For other MAX_ORDER uses (described below), there is no need or too much
> hassle to convert certain static array to dynamic ones. Add
> MIN_MAX_ORDER to serve as compile time constant in place of MAX_ORDER.
>
> ARM64 hypervisor maintains its own free page list and does not import
> any core kernel symbols, so soon-to-be runtime variable MAX_ORDER is not
> accessible in ARM64 hypervisor code. Also there is no need to allocating
> very large pages.
>
> In SLAB/SLOB/SLUB, 2-D array kmalloc_caches uses MAX_ORDER in its second
> dimension. It is too much hassle to allocate memory for kmalloc_caches
> before any proper memory allocator is set up.
>
> Signed-off-by: Zi Yan <ziy@...dia.com>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Quentin Perret <qperret@...gle.com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: kvmarm@...ts.cs.columbia.edu
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> ---
> arch/arm64/kvm/hyp/include/nvhe/gfp.h | 2 +-
> arch/arm64/kvm/hyp/nvhe/page_alloc.c | 3 ++-
> include/linux/mmzone.h | 3 +++
> include/linux/slab.h | 8 ++++----
> mm/slab.c | 2 +-
> mm/slub.c | 7 ++++---
> 6 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/gfp.h b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> index fb0f523d1492..c774b4a98336 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> @@ -16,7 +16,7 @@ struct hyp_pool {
> * API at EL2.
> */
> hyp_spinlock_t lock;
> - struct list_head free_area[MAX_ORDER];
> + struct list_head free_area[MIN_MAX_ORDER];
> phys_addr_t range_start;
> phys_addr_t range_end;
> unsigned short max_order;
> diff --git a/arch/arm64/kvm/hyp/nvhe/page_alloc.c b/arch/arm64/kvm/hyp/nvhe/page_alloc.c
> index 41fc25bdfb34..a1cc1b648de0 100644
> --- a/arch/arm64/kvm/hyp/nvhe/page_alloc.c
> +++ b/arch/arm64/kvm/hyp/nvhe/page_alloc.c
> @@ -226,7 +226,8 @@ int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages,
> int i;
>
> hyp_spin_lock_init(&pool->lock);
> - pool->max_order = min(MAX_ORDER, get_order(nr_pages << PAGE_SHIFT));
> +
> + pool->max_order = min(MIN_MAX_ORDER, get_order(nr_pages << PAGE_SHIFT));
> for (i = 0; i < pool->max_order; i++)
> INIT_LIST_HEAD(&pool->free_area[i]);
> pool->range_start = phys;
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 09aafc05aef4..379dada82d4b 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -27,11 +27,14 @@
> #ifndef CONFIG_ARCH_FORCE_MAX_ORDER
> #ifdef CONFIG_SET_MAX_ORDER
> #define MAX_ORDER CONFIG_SET_MAX_ORDER
> +#define MIN_MAX_ORDER CONFIG_SET_MAX_ORDER
> #else
> #define MAX_ORDER 11
> +#define MIN_MAX_ORDER MAX_ORDER
> #endif /* CONFIG_SET_MAX_ORDER */
> #else
> #define MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
> +#define MIN_MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
> #endif /* CONFIG_ARCH_FORCE_MAX_ORDER */
> #define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1))
The end result of this #ifdef explosion looks entirely unreadable:
/* Free memory management - zoned buddy allocator. */
#ifndef CONFIG_ARCH_FORCE_MAX_ORDER
#ifdef CONFIG_SET_MAX_ORDER
/* Defined in mm/page_alloc.c */
extern int buddy_alloc_max_order;
#define MAX_ORDER buddy_alloc_max_order
#define MIN_MAX_ORDER CONFIG_SET_MAX_ORDER
#else
#define MAX_ORDER 11
#define MIN_MAX_ORDER MAX_ORDER
#endif /* CONFIG_SET_MAX_ORDER */
#else
#ifdef CONFIG_SPARSEMEM_VMEMMAP
/* Defined in mm/page_alloc.c */
extern int buddy_alloc_max_order;
#define MAX_ORDER buddy_alloc_max_order
#else
#define MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
#endif /* CONFIG_SPARSEMEM_VMEMMAP */
#define MIN_MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
#endif /* CONFIG_ARCH_FORCE_MAX_ORDER */
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 2c0d80cca6b8..d8747c158db6 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -244,8 +244,8 @@ static inline void __check_heap_object(const void *ptr, unsigned long n,
> * to do various tricks to work around compiler limitations in order to
> * ensure proper constant folding.
> */
> -#define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
> - (MAX_ORDER + PAGE_SHIFT - 1) : 25)
> +#define KMALLOC_SHIFT_HIGH ((MIN_MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
> + (MIN_MAX_ORDER + PAGE_SHIFT - 1) : 25)
> #define KMALLOC_SHIFT_MAX KMALLOC_SHIFT_HIGH
> #ifndef KMALLOC_SHIFT_LOW
> #define KMALLOC_SHIFT_LOW 5
> @@ -258,7 +258,7 @@ static inline void __check_heap_object(const void *ptr, unsigned long n,
> * (PAGE_SIZE*2). Larger requests are passed to the page allocator.
> */
> #define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1)
> -#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1)
> +#define KMALLOC_SHIFT_MAX (MIN_MAX_ORDER + PAGE_SHIFT - 1)
> #ifndef KMALLOC_SHIFT_LOW
> #define KMALLOC_SHIFT_LOW 3
> #endif
> @@ -271,7 +271,7 @@ static inline void __check_heap_object(const void *ptr, unsigned long n,
> * be allocated from the same page.
> */
> #define KMALLOC_SHIFT_HIGH PAGE_SHIFT
> -#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1)
> +#define KMALLOC_SHIFT_MAX (MIN_MAX_ORDER + PAGE_SHIFT - 1)
> #ifndef KMALLOC_SHIFT_LOW
> #define KMALLOC_SHIFT_LOW 3
> #endif
> diff --git a/mm/slab.c b/mm/slab.c
> index d0f725637663..0041de8ec0e9 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -466,7 +466,7 @@ static int __init slab_max_order_setup(char *str)
> {
> get_option(&str, &slab_max_order);
> slab_max_order = slab_max_order < 0 ? 0 :
> - min(slab_max_order, MAX_ORDER - 1);
> + min(slab_max_order, MIN_MAX_ORDER - 1);
> slab_max_order_set = true;
>
> return 1;
> diff --git a/mm/slub.c b/mm/slub.c
> index b6c5205252eb..228e4a77c678 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3564,8 +3564,9 @@ static inline int calculate_order(unsigned int size)
> /*
> * Doh this slab cannot be placed using slub_max_order.
> */
> - order = slab_order(size, 1, MAX_ORDER, 1);
> - if (order < MAX_ORDER)
> +
> + order = slab_order(size, 1, MIN_MAX_ORDER, 1);
> + if (order < MIN_MAX_ORDER)
> return order;
> return -ENOSYS;
> }
> @@ -4079,7 +4080,7 @@ __setup("slub_min_order=", setup_slub_min_order);
> static int __init setup_slub_max_order(char *str)
> {
> get_option(&str, (int *)&slub_max_order);
> - slub_max_order = min(slub_max_order, (unsigned int)MAX_ORDER - 1);
> + slub_max_order = min(slub_max_order, (unsigned int)MIN_MAX_ORDER - 1);
>
> return 1;
> }
> --
> 2.30.2
>
--
Sincerely yours,
Mike.
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